This invention relates to novel copolymer compositions, method of preparing same, non-aqueous coating compositions and compositions in a non-aqueous system which are useful as liquid toners for electrophotography. More particularly, this invention relates to copolymer compositions prepared by copolymerization of low molecular weight esters such as vinyl esters and long chain, C.sub.6 to C.sub.20 aliphatic ethylenically unsaturated esters in an isoparaffinic hydrocarbon solvent.
The use of liquid developers for electrophotography, i.e., rendering visible as a permanent image a latent image consisting of a pattern of electrostatic charges, is well known. The use of liquid toners over the dry method of developing such a pattern of charges has advantages such as, for example, sharper and better defined images, images having a higher degree of economical use of the developer, a faster developing cycle, and simpler less expensive and more trouble free developing equipment. However, although the industry strongly desires an excellent liquid toner, those which presently are available are subject to various deficiencies. For example, the liquid toners heretofore available have not given sufficiently good resolution or sufficiently dense or sharp images. In addition, with many liquid toners there has been a serious complaint that shelf life was not long enough in that some of the solids suspended within the liquid toner tended to settle and agglomerate too quickly making it necessary to redisperse them prior to use. This is especially true with respect to pigment containing liquid toners.
In addition to the toner problems described above, conventional electrophotography has a disadvantage of giving copies which lack the feel and look of plain bond paper and lack the contrast of offset printed material. However there is a trend today towards the development of so-called copier/duplicators which combine in one machine the advantages of both electrophotography and offset printing. In such machines a lithographic plate is prepared by an electrophotographic process in which a photoconductor coated substrate is charged in the dark, exposed to an original image, toned with a so-called lithographic toner and subsequently chemically treated to render the image areas oleophilic and hydrophobic and the non-image areas hydrophilic and oleophobic as is normally done in any offset process. It is therefore possible by the use of such copier/duplicator machines to generate offset quality copies by an electrophotographic process.
The major requirement in such copier/duplicator machines is the lithographic toner that is to be used.